Corrosion of rebar in concrete. Part IV. On the theoretical basis of the chloride threshold

A theory is developed for calculating the chloride threshold (CT) from the Point Defect Model (PDM). CT is defined as the ratio [Cl − ]/[OH − ] at which the passivity breakdown voltage ( E b ) equals the corrosion potential, ECP . CT is sensitive to the T , ECP, pH, and E b , because all four appear in the exponent X in CT = 10 X . Small uncertainties in these parameters translate into a large uncertainty in CT, emphasizing the need for accurate T , ECP, pH, and E b data. We demonstrate the theory by successfully calculating CT using data for selected systems.